TOC by Sipser is incorrect at some points, especially in Push Down Automata. I will instead recommend the `Automata Theory Language & Computation` by Ullman et al.
Don't do this. While Sipser has a couple of hipccups he is a MUCH better teacher and writer. Ullman et al are brilliant and all but their writing is both boring and incomprehensible. I am not even talking about the most useless recommendation of them all - the Dragon book.